The present invention relates generally to fittings, such as fittings for interconnecting sections of conduit, and more particularly relates to transfer fittings that are shielded from electromagnetic interference (xe2x80x9cEMIxe2x80x9d).
Fittings are well known. One particular application for various types of fittings is to interconnect sections of conduit that carryelectrical wires or cables, such as power cables and/or bundles of data cables. (It is to be understood by those of skill in the art that, in the present application, the terms xe2x80x9cwiresxe2x80x9d and xe2x80x9ccablesxe2x80x9d can generally refer to any type of conductor, suitable for a particular application, that is carried through a section of conduit). With society""s greater reliance on dependable electronic data exchange, bundles of data cables that form the backbone of networks are now ubiquitous, and electromagnetic compatibility can be an important requirement in the design of the cables and the conduits that carry them. Bundles of data cables are now frequently run through fixed structures, such as houses, skyscrapers, and through vehicles such as cars, trucks, aircraft, naval ships, submarines or any other type of like-installation.
When running data cables through structures, vehicles and other locations it is important to provide adequate mechanical protection and/or EMI protection, depending on the particular needs of the data cable and the types of environmental hazards to which the cable may be exposed. Whereas prior art conduits used for power cables were primarily designed to provide mechanical protection, more modem data cables can be greatly suceptible to EMI, which can greatly degrade and/or otherwise impair proper functioning of the computer network that the data cable supports.
In submarines, data cables can be succeptible to a wide variety of mechanical and EMI stresses that are particularly unique to the submarine environment, and thus, prior art fittings for interconnecting sections of conduit, either of the same or different types, have proven to be unsuccesful in providing the desired and/or necessary robustness, thereby resulting in failure of the onboard computer networks. As will be well understood by any sailor in a combat situation, such failure could cost the sailor his or her life. Mechanical stresses peculiar to submarines can include torsional stresses on the hull of the ship, which thereby stresses any conduit runs, and fittings interconnecting such conduit. Further mechanical stresses can include exposure to water, particularly when, as in the case of a naval vessel, conduits are being cleaned using high-pressure water spray. Conduits must thus be able to withstand the pressure of the waterspray while protecting the cable and the sheathing running through the inside the conduit. EMI stresses on submarines can also be unique, such as the need to protect the data cables running through the submarine from external EMI caused by floating ground connections, and from the movement of the submarine through external magnetic fields. Additionally, it is considered important to shield data cables from emitting their own EMI, which could interfere with SONAR readings and/or adjacent data cables.
An additional problem with prior art transfer fittings arises when retrofitting older structures or installations, such as submarines, with modem bundles of data cables. During such retrofits, it is often necessary to affix a transfer fitting to the end of a piece of unthreaded conduit. Such unthreaded conduit can be found in portions of the vessel where a continuous piece of conduit must be cut in order to feed the cable through the conduit, thus leaving an exposed piece of conduit with an unthreaded end, making conventional, complementary threaded transfer fittings unusable. Thus, the aforementioned disadvantages of the prior art are compounded when attaching a transfer fitting to an unthreaded piece of conduit.
It is therefore desirable to have a robust transfer fitting for interconnecting conduits that can withstand high stress environments, including both mechanical and EMI stresses.
It is therefore an object of the invention to provide a novel EMI transfer fitting that obviates or mitigates at least one of the disadvantages of the prior art.
In an aspect of the invention, there is provided an EMI transfer fitting comprising a first coupler for connection to an unthreaded rigid conduit for carrying a cable bundle. The EMI transfer fitting also has a second coupler for connection to a second piece of conduit. The first coupler has a first male fastener, a compression ring and a first female fastener for receiving the rigid conduit therethrough. One of the fasteners is at a distal end adjacent to the rigid conduit and the other of the fasteners is at a proximal end that is opposite the distal end. The first male fastener and the first female fastener have a first cooperating tightening means for urging the first male fastener towards the second female fastener, such that when said first fasteners are tightened, the compression ring has external pressure applied thereto and thereby securely grasping the rigid conduit within the first coupler.
In a second aspect of the invention, there is provided an EMI transfer fitting comprising a first coupler for connection to a first piece of conduit. The first coupler has a distal end that connects with the first piece of conduit, and a proximal end opposite from the distal end. The EMI transfer fitting of the second aspect has a second coupler attached to the proximal end, the second coupler having an attachment means for connecting to a flexible conduit for carrying a sheathed cable therein, the second coupler further having a second male fastener, a hollow insert for passing the cable therethrough and passing said sheath thereover, and a second female fastener, the second male fastener and the second female fastener having a second cooperating tightening means for urging the second male fastener towards the second female fastener, such that when the second fasteners are tightened the sheath is impinged between an exterior of the insert and an interior of the second coupler.
In a third aspect of the invention, the first two aspects are combined into a single transfer fitting.
An EMI transfer fitting suitable for use in submarines and other harsh environments is provided. In one embodiment, the EMI transfer fitting has two couplers, that collectively provide a mechanically robust interconnection between a flexible conduit (through which a bundle of data cables is encased by a wire mesh sheath that provides EMI shielding), and a rigid conduit made from a metallic material that requires no separate wire mesh sheath to provide EMI shielding. In addition to providing a robust mechanical interconnection, the transfer fitting provides a robust and seamless EMI shielding between the flexible conduit and the rigid conduit.